A number of techniques have been proposed in terms of so-called onboard diagnosis (hereinafter referred to as OBD) detecting air-fuel ratio variation (air-fuel ratio imbalance) between cylinders of an engine, catalyst deterioration in an exhaust gas purifier, etc. For example, in a technique disclosed in a hybrid vehicle of Patent Document 1, when the air-fuel ratio imbalance is detected between cylinders of an engine, OBD is performed after an engine power is put into a steady state.